Carbon nanotube and carbon nanohorn aggregate have been receiving keen attention as novel nano-structure substances which are potentially useful in a variety of fields such as information channel industry, chemical industry, and the like. There has been conducted a variety of applicative studies for utilizing characteristics of carbon nanotube and carbon nanohorn aggregate.
A carbon nanotube is a cylindrical carbon substance whose diameter is approximately 1 to 10 nm and length is a few micrometer. A carbon nanotube has a very regular, continuous structure of six-member rings. It is expected that utilization of the minute and unique form and electrical properties of a carbon nanotube will enable various applications thereof such as an application to a material for a fuel cell.
A carbon nanohorn aggregate is an aggregate in which plural carbon nanohorns, the tip end of each of which nanohorns has a horn-like sharp shape which would be obtained by sharpening a tip end of a carbon nanotube such that the tip end angle thereof is approximately 20°, are radially aggregated with a conical tip portion of each carbon nanohorn being disposed on the outer side, thereby forming a spherical complex whose diameter is approximately 100 nm. It is considered that such a carbon nanohorn aggregate is applicable to an adsorbing material or the like, by utilizing the aforementioned unique structure and a characteristic thereof of selectively adsorbing various types of gases.
With regard to the production of carbon nanotube and carbon nanohorn aggregate described above, there have been proposed several production methods which can achieve a high yielding rate. However, when carbon nanotubes are mass-produced, the produced carbon nanotubes tend to form bundles in which several tens of carbon nanotubes are aggregated with each other due to van der Waals force generated therebetween, and it is hardly possible to maintain the produced carbon nanotubes in a state in which the carbon nanotubes are each independently dispersed. In the case of carbon nanohorn aggregate, carbon nanohorn aggregates, which are very light carbon ultra-fine particles, can be easily dispersed in a solvent, even when the carbon nanohorn aggregates are mass-produced. However, in a case in which carbon nanohorn aggregates are solely dispersed in a solvent, the carbon nanohorn aggregates tend to be closely aggregated with each other, thereby causing a problem in that the structure specific to the carbon nanohorn aggregate cannot be effectively utilized.
In view of the above-described circumstances, one object of the invention of the present application is to provide a novel carbon nanotube-carbon nanohorn complex which solves the problems of the prior art, enables more effective utilization of a surface of a carbon nanotube and that of a carbon nanohorn aggregate and enlarges a scope of applicability thereof. The invention also provides a method for producing the same.